The invention relates to a method of operating and monitoring a group of filter membrane modules, and also to a group of modules implementing the method, with a particular application to filtering water.
It has long been the practice to obtain potable water from natural waters (lakes, rivers) that are polluted to a greater or lesser extent, and to do so by means of installations that are fixed, given the techniques used. The recent appearance of filter membranes disposed in bundles within filter modules has made it possible to implement mobile installations suitable for taking action in the event of a fixed installation failing or in an emergency, e.g. when providing humanitarian aid.
Known mobile installations operate with pumps, including at least a booster pump and a pump for backwashing the membranes, which pumps consume a great deal of electricity. In some cases, installations are required to operate in areas without electricity so it is necessary to provide generator units and the fuel required to run them.
In addition, it is difficult to monitor the operation of filter modules, and if anomalies are observed to appear, it is very difficult or even impossible to find out the exact cause: excessive clogging, or membrane rupture in a module, and if so in which module, backwashing failure in a module, etc. . . .
Such installations usually operate on demand, i.e. they periodically stop production. When they are designed for temporary operation, they must also be capable of remaining unharmed during long periods of no operation. In both cases it is necessary to provide for the circuits to be chlorinated in order to avoid bacteria proliferating since that could damage the membranes or could be dangerous when the installation is put back into operation. Chlorination is performed by periodically injecting chlorinated water into the circuits by pumping.
In an emergency situation, the water to be treated may be unusually polluted and it is often necessary not only to perform periodic backwashing, but also to perform cleaning using appropriate cleaning substances. It is therefore necessary for the installation to be fitted with a cleaning circuit, and that requires a pump.
A water treatment assembly must therefore satisfy the following needs:
it must be compact, i.e. its volume must be small compared with its production capacity so as to facilitate transport thereof; PA1 it must consume only a small amount of electricity, so it must have as few pumps as possible; PA1 advantageously it should have a chlorination circuit and a cleaning circuit; and PA1 it should make it possible to diagnose possible operating anomalies and the state of the filter membranes, and to proceed with appropriate corrective action. PA1 raw water to be treated is injected into the group of modules at a regulated pressure and the outlet pressure of the permeate (filtered water) is regulated to a value that is lower than that of the inlet pressure, but nevertheless sufficient to enable the filter membrane modules to be backwashed; PA1 the group of modules is provided with a water meter on the raw water inlet duct and with three pressure sensors, a first on the raw water inlet, a second on the permeate outlet, and a third on the backwashing circuit, the meter and the sensors delivering signals to a controller; PA1 the modules are backwashed successively one after another, using the permeate from the other modules, thereby individualizing each module while it is being backwashed, thus making it possible with the water meter and the pressure sensors to determine the permeability in backwashing specific to the module thus individualized, and also to determine the production permeability of the remaining modules; and PA1 the permeability values obtained in this way are compared with ideal values, with threshold values, and/or with values from earlier cycles so that, depending on the diagnosis obtained, the periodicity of backwashing is modified, the group of modules is cleaned, or an operating anomaly is detected, thereby enabling it to be corrected. PA1 (Lp).sub.i in backwashing for each of the modules in succession; and PA1 (Lp).sub.n-i in production for the set of modules minus the module that is being backwashed. PA1 excessive clogging which means that the set of modules must be cleaned, with the difference between permeability in filtering and permeability in backwashing also making it possible to select between available cleaning substances; PA1 rupture of the filter membranes in a module, which means that the module must be taken out of operation and replaced; and PA1 abnormal operation of a valve.